Dual thrust bearing for a turbocharger

ABSTRACT

A dual thrust bearing is disclosed. The dual thrust bearing may have a shell. The shell may extend from a compressor end to a turbine end opposite the compressor end. The shell may have a shell bore extending from the compressor end to the turbine end. The shell bore may be configured to receive a journal bearing. The shell may also have a first thrust bearing face disposed adjacent the compressor end. In addition, the shell may have a second thrust bearing face disposed adjacent the turbine end.

TECHNICAL FIELD

The present disclosure relates generally to a dual thrust bearing and, more particularly, to a dual thrust bearing for a turbocharger.

BACKGROUND

Internal combustion engines, for example, diesel engines, gasoline engines, or natural gas engines employ turbochargers to deliver compressed air for combustion in the engine. A turbocharger compresses air flowing into the engine, helping to force more air into combustion chambers of the engine. The increased supply of air allows for increased fuel combustion in the combustion chambers of the engine, resulting in an increased power output from the engine.

A typical turbocharger includes a shaft, a turbine wheel connected to one end of the shaft, a compressor wheel connected to the other end of the shaft, and bearings to support the shaft. Separate housings connected to each other enclose the compressor wheel, the turbine wheel, and the bearings. Exhaust from the engine expands over the turbine wheel and rotates the turbine wheel. The turbine wheel in turn rotates the compressor wheel via the shaft. The compressor wheel receives cool air from the ambient and forces compressed air into combustion chambers of the engine.

The flows of exhaust and compressed air over the turbine wheel and the compressor wheel, respectively, exert radial and axial loads on the shaft. Turbochargers typically include at least two separate journal bearings and two separate thrust bearings to counter the radial and axial loads, respectively, generated by the compressor and turbine portions of the turbocharger. Proper functioning of the turbocharger requires accurate positioning or centering of the different types of bearings within the bearing housing. Maintaining two separate thrust bearings, however, adds complexity and increases the volume of the turbocharger. In particular, use of separate bearings increases the dimensional tolerance stack for the turbocharger, requiring larger clearances between the rotating parts. The larger clearances in turn make it difficult to minimize leakage of oil from the turbocharger to the ambient and leakage of dust and ambient air into the turbocharger.

One attempt to address some of the problems described above is disclosed in U.S. Pat. No. 6,017,184 of Aguilar et al. that issued on Jan. 25, 2000 (“the '184 patent”). In particular, the '184 patent discloses an integrated bearing system with journal and thrust bearings incorporated in a single unit centrally pinned to the bearing housing. The '184 patent discloses that the bearing is carried within a bearing case bore of the center housing and that thrust surfaces are located at opposite ends of the bearing. One thrust surface of the bearing engages a thrust runner on the turbine wheel hub, whereas the other thrust surface of the bearing engages a thrust surface integrated into the hub of a compressor wheel.

Although the '184 patent discloses an integrated bearing that includes a journal bearing and thrust surfaces on opposing ends of the bearing, the disclosed bearing may still be less than optimal. In particular, thrust loads on the bearing of the '184 patent may be reacted on the alignment pin or on a shoulder of the center housing. Unequal thrust loads on the two thrust faces of the bearing of the '184 patent may skew the bearing relative to an axis of rotation of the bearing, which in turn may constrain the rotation of the shaft within the journal portion of the bearing. In addition, because the integrated bearing of the '184 patent directly attaches to the center housing, a typical rotor failure may damage both the bearing and the mounting surfaces of the center housing, requiring expensive and time consuming repairs or replacement of the center housing.

The dual thrust bearing of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.

SUMMARY

In one aspect, the present disclosure is directed to a dual thrust bearing. The dual thrust bearing may include a shell. The shell may extend from a compressor end to a turbine end opposite the compressor end. The shell may include a shell bore extending from the compressor end to the turbine end. The shell bore may be configured to receive a journal bearing. The shell may also include a first thrust bearing face disposed adjacent the compressor end. In addition, the shell may include a second thrust bearing face disposed adjacent the turbine end.

In another aspect, the present disclosure is directed to a bearing assembly. The bearing assembly may include a shell extending from a compressor end to a turbine end opposite the compressor end. The bearing assembly may also include a shell bore extending from the compressor end to the turbine end. Further, the bearing assembly may include a first thrust bearing face disposed on the compressor end of the shell. The bearing assembly may also include a second thrust bearing face disposed on the turbine end of the shell. In addition, the bearing assembly may include a journal bearing disposed within the shell bore

In yet another aspect, the present disclosure is directed to a turbocharger. The turbocharger may include a turbine housing. The turbocharger may also include a turbine wheel disposed within the turbine housing. The turbine wheel may be configured to be rotated by exhaust received from an engine. The turbocharger may also include a compressor housing. Further the turbocharger may include a shaft attached to the turbine wheel. The shaft may extend from the turbine housing to the compressor housing. A compressor impeller may be disposed within the compressor housing. The compressor impeller may be configured to be driven by the turbine wheel via the shaft. The turbocharger may include a bearing housing connecting the turbine housing with the compressor housing. The turbocharger may also include a bearing assembly disposed within the bearing housing. The bearing assembly may include a shell extending from the compressor end to the turbine end. The bearing assembly may also include a shell bore in the shell extending from the compressor end to the turbine end. Further, the bearing assembly may include a journal bearing extending from a compressor end to a turbine end. The journal bearing may be disposed within the shell bore. The bearing assembly may include a thrust washer disposed on the shaft adjacent the turbine end. The bearing assembly may also include a first thrust bearing face disposed on the compressor end of the shell. The first thrust bearing face may be axially separated from the compressor impeller by a first gap. The bearing assembly may further include a second thrust bearing face disposed on the turbine end of the shell. The second thrust bearing face may be axially separated from the thrust washer by a second gap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cut-away view of an exemplary disclosed turbocharger;

FIG. 2 is a cut-away view of an exemplary disclosed bearing assembly for the turbocharger of FIG. 1;

FIG. 3 is a cut-away view of an exemplary disclosed dual thrust bearing for the turbine bearing assembly of FIG. 2;

FIG. 4 is a cut-away view of an exemplary disclosed thrust bearing face of the dual thrust bearing of FIG. 3;

FIG. 5 is another cut-away view of the exemplary disclosed thrust bearing face of FIG. 4; and

FIG. 6 is a cut away view of another exemplary disclosed thrust bearing face of the dual thrust bearing of FIG. 3.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary embodiment of a turbocharger 10. Turbocharger 10 may be used with an engine (not shown) of a machine that performs some type of operation associated with an industry such as railroad, marine, power generation, mining, construction, farming, or another industry known in the art. As shown in FIG. 1, turbocharger 10 may include compressor stage 12 and turbine stage 14. Shaft 16 may extend between compressor stage 12 and turbine stage 14. Shaft 16 may be supported by one or more bearing assemblies 18 and/or bearings 20. Compressor stage 12 may embody a fixed geometry compressor impeller 22 connected to shaft 16 and configured to compress air received from an ambient to a predetermined pressure level before the air enters the engine for combustion. Air may enter compressor housing 24 via compressor inlet 26 and exit compressor housing 24 via compressor outlet 28. As air moves through compressor stage 12, compressor impeller 22 may force compressed air into the engine. Compressing the air may heat the air, which in turn may heat compressor impeller 22, compressor housing 24, bearing housing 38, and other components of the turbocharger located near compressor stage 12.

Turbine stage 14 may be a fixed geometry turbine. Turbine stage 14 may include turbine housing 30 and turbine wheel 32, which may be attached to shaft 16. Exhaust gases exiting the engine may enter turbine housing 30 via turbine inlet 34 and exit turbine housing 30 via turbine outlet 36. As the hot exhaust gases move through turbine housing 30 and expand against the blades of turbine wheel 32, turbine wheel 32 may rotate compressor impeller 22 via shaft 16. The hot exhaust gases may also heat turbine housing 30, which in turn may heat compressor housing 24, bearing housing 38, and other components of the turbocharger attached to or located near turbine housing 30.

FIG. 2 illustrates a cut-away view of an exemplary embodiment of a bearing assembly 18 for turbocharger 10. Bearing assembly 18 may include bearing housing 38, dual thrust bearing 50, journal bearing 52, alignment pin 54, impeller cap 56, and thrust washer 58. Bearing housing 38, dual thrust bearing 50, journal bearing 52, alignment pin 54, impeller cap 56, and thrust washer 58 may be disposed around a rotational axis 60 of bearing assembly 18. As illustrated in FIG. 2, bearing housing 38 may engage with dual thrust bearing 50 at first bore 70 and second bore 72. Bearing housing 38 may also include a wall 74, which may extend radially towards rotational axis 60. Wall 74 may have a front face 78 and a rear face 80. Wall 74 may include one or more fastener holes 76, which may extend from front face 78 to rear face 80 of wall 74. Fastener hole 76 may be configured to receive fastener 82, which may be configured to attach dual thrust bearing 50 to bearing housing 38. Bearing housing 38 may also include an alignment cavity 84 that may extend axially from front face 78 of wall 74 towards rear face 80 to a depth “l₁,” which may be shorter than a thickness “l₂” of wall 74. Alignment cavity 84 may be generally cylindrical and may have a longitudinal axis 86, which may be disposed generally parallel to rotational axis 60.

Dual thrust bearing 50 may include shell 100 that may extend from compressor end 102 to turbine end 104. Shell 100 may include a generally cylindrical shell bore 106 that may extend from compressor end 102 to turbine end 104. Shell bore 106 may be configured to receive journal bearing 52. Shell 100 may include a flange 108 that may be configured to mount dual thrust bearing 50 to bearing housing 38. Flange 108 may be disposed adjacent compressor end 102. Flange 108 may have a flange front face 110 and a flange rear face 112 opposite flange front face 110. Flange rear face 112 may be disposed between flange front face 110 and turbine end 104. Flange 108 may have a thickness “l₃,” which may be smaller than a length “L” of shell 100. Flange 108 may have a flange outer surface 114 that may engage with first bore 70 of bearing housing 38. In one exemplary embodiment, flange outer surface 114 may engage with first bore 70 of bearing housing 38 via an interference fit. It is contemplated, however, that flange outer surface 114 may engage with first bore 70 of bearing housing 38 via a clearance fit.

Flange 108 may also include one or more fastener holes 116. In one exemplary embodiment as illustrated in FIG. 2, fastener hole 116 may be a stepped through hole, which may be configured to receive fastener 82. Fastener 82 may pass through fastener hole 116 in flange 108 and fastener hole 76 in wall 74 of bearing housing 38. Fastener 82 may threadingly engage with threaded hole 118 in back plate 120 to attach dual thrust bearing 50 to bearing housing 38. Although FIG. 2 illustrates only one back plate 120, it is contemplated that bearing assembly 18 may include any number of back plates 120, each of which may include threaded holes 118 configured to threadingly engage with fasteners 82. It is also contemplated that flange 108 may be attached to wall 74 of bearing housing 38 using bolts (not shown) that may engage with fasteners 82.

Shell 100 may also include a hub 130 disposed adjacent turbine end 104. Hub 130 may have a hub front face 132 and a hub rear face 134 opposite hub front face 132. Hub front face 132 may be disposed between hub rear face 134 and flange rear face 112. Hub 130 may have an axial length “l₄” between hub front face 132 and hub rear face 136. Length l₄ may be smaller than length L of shell 100. Hub 130 may have a hub outer surface 136 that may engage with second bore 72 of bearing housing 38 via a clearance fit. Hub 130 may also include a circumferential groove 138 disposed on hub outer surface 136. Seal member 140 may be disposed within groove 138 between hub outer surface 136 and second bore 72 of bearing housing 38. In one exemplary embodiment as illustrated in FIG. 2, seal member 140 may be an O-ring. It is contemplated, however, that seal member 140 may be a gasket or any other type of sealing element known in the art.

Shell 100 may have a first thrust bearing face 142 adjacent compressor end 102. First thrust bearing face 142 may be disposed on flange front face 110 of shell 100. First thrust bearing face 142 may be axially separated from compressor impeller 22 by first gap 144. Shell 100 may also have a second thrust bearing face 146 disposed adjacent turbine end 104. Second thrust bearing face 146 may be disposed on hub rear face 134. Second thrust bearing face 146 may be axially separated from thrust washer 58 by second gap 148. Shell 100 may include a recess 150 disposed between flange rear face 112 and to hub front face 132. Recess 150 may be generally annular and may have a recess inner surface 152 that may have an outer diameter “D₁,” which may be smaller than a diameter “D₂” of hub outer surface 136. Pressurized oil may be supplied from an oil pump (not shown) via passageways (not shown) in bearing housing 38 to recess 150. Oil may flow from recess 150 through passageways (not shown) in shell 100 to shell bore 106 and first and second thrust bearing faces 142, 146.

Journal bearing 52 may be disposed within shell bore 106 between compressor end 102 and turbine end 104. Journal bearing 52 may have a generally cylindrical shape, which may have a journal outer surface 152 and a journal inner surface 154. Journal outer surface 152 may engage with shell bore 106 via an interference fit. It is contemplated, however, that journal outer surface 152 may engage with shell bore 106 via a clearance fit. Journal bearing 52 may include pin recess 156 disposed on journal outer surface 152. Pin recess 156 may be configured to receive alignment pin 54. Pin recess 156 may have a generally cylindrical shape. It is contemplated, however, that pin recess 158 may have an elliptical, triangular, square, polygonal or any other shape known in the art.

Alignment pin 54 may have a knob portion 162, which may be received in alignment cavity 84. In one exemplary embodiment as illustrated in FIG. 2, knob portion 162 of alignment pin 54 may have a generally spherical shape, which may be configured to slidingly engage with alignment cavity 84. It is contemplated, however, that knob portion 162 of alignment pin 54 may have an oval, cuboidal, or any other shape that matches a shape of the alignment cavity 84. Alignment pin 54 may extend from the knob portion to a stud portion 164, which may engage with pin recess 158 via an clearance fit. Stud portion 164 of alignment pin 54 may have a cross-section that matches a shape of pin recess 156 to allow engagement of alignment pin 54 with journal bearing 52. In one exemplary embodiment as illustrated in FIG. 2, knob portion 162 of alignment pin 54 may engage with alignment cavity 84 to help prevent rotation of journal bearing 52 around rotational axis 60. Alignment cavity 84 may also limit lateral movement of alignment pin 54 along rotational axis 60, which may help prevent axial movement of journal bearing 52 within dual thrust bearing 50.

Compressor impeller 22 may include an impeller cap 56, which may include a cap portion 166 and a shaft portion 168. Cap portion 166 of impeller cap 56 may be connected to compressor impeller 22 so that compressor impeller 22 rotates with impeller cap 56. Shaft portion 168 of impeller cap 56 may be attached to cap portion 166. Shaft portion 168 of impeller cap 56 may be disposed within journal bearing 52. Cap portion 166 of impeller cap 56 may have an outer diameter “D₃,” which may be larger than an outer diameter “D₄” of shaft portion 168 of impeller cap 56. Cap portion 166 of impeller cap 56 may transition from diameter D₁ to diameter D₂ of shaft portion 168 via impeller step 170. Impeller step 170 may have an impeller step face 172, which may be disposed opposite to and spaced apart from first thrust bearing face 142 of dual thrust bearing 50. In one exemplary embodiment as illustrated in FIG. 2, impeller step face 172 may be separated from first thrust bearing face 142 via first gap 144.

Impeller cap 56 may also include an impeller cap bore 176 configured to receive shaft 16. Shaft 16 may engage with impeller cap bore 176 via an interference fit, a keyed joint, a welded joint, a threaded joint, or by any other type of attachment known in the art. Shaft 16 may include shaft step 178 disposed adjacent turbine end 104. Shaft 16 may transition from a diameter “D₅” within impeller cap bore 176 to a diameter “D₆” adjacent turbine end 104. In one exemplary embodiment as shown in FIG. 2, diameter D₆ may be larger than diameter D₅. Shaft step 178 may have shaft step face 180 disposed opposite to and axially separated from hub rear face 134.

Thrust washer 58 may be disposed on shaft portion 168 of impeller cap 56 adjacent turbine end 104. In one exemplary embodiment as illustrated in FIG. 2, thrust washer 58 may be disposed between shaft step face 180 and hub rear face 134. Thrust washer 58 may be attached to shaft portion 168 and may be configured to rotate with shaft 16. Thrust washer 58 may be attached to shaft 16 via an interference fit, a keyed joint, a welded joint, a threaded joint, or by any other type of attachment known in the art. Thrust washer 58 may have a thrust washer front face 182 and a thrust washer rear face 184. Thrust washer front face 182 may be disposed adjacent to and axially spaced apart from second thrust bearing face 146 via second gap 148. Thrust washer rear face 184 may abut shaft step face 180. Pressurized oil may flow via passageways (not shown) in shell 100 to first and second gaps 144, 148. Pressurized oil in first and second gaps 144, 148 may flow circumferentially and radially over first and second thrust bearing faces 142, 146, respectively to help counter axial loads on shaft 16.

FIG. 3 illustrates a cut-away view showing portions of first thrust bearing face 142. First thrust bearing face 142 may extend radially between an inner wall 192 and an outer wall 194. Inner wall 192 may have a diameter smaller than a diameter of outer wall 194. First thrust bearing face 142 may include a plurality of thrust pad sections 196 circumferentially disposed on first thrust bearing face. Adjacent thrust pad sections 196 may be circumferentially separated by radially extending drains 198. Each thrust pad section 196 may extend circumferentially from a leading end 200 to a trailing end 202. Thrust pad section 196 may include slot 204, thrust pad 206, ramp 208, and rim 210. Slot 204 may be disposed adjacent leading end 200 of thrust pad section 196. In one exemplary embodiment as illustrated in FIG. 3, slot 204 may extend radially from an inner slot end 212 disposed adjacent inner wall 192 to an outer slot end 214 disposed adjacent outer wall 194. As illustrated in FIG. 3, inner slot end 212 and outer slot end 214 may not extend all the way to inner wall 192 and outer wall 194, respectively. Slot 204 may also have rounded edges at inner and outer slot ends 212, 214. Slot 204 may be shallow relative to thickness l₃ of flange 108. Slot 204 may include an inlet 216. In one exemplary embodiment as illustrated in FIG. 3, inlet 216 may be disposed nearer inner slot end 212 compared to outer slot end 214. Inlet 216 may have a generally circular shape. It is contemplated, however, that inlet 216 may have an elliptical, polygonal, or any other type of shape known in the art. Inlet 216 may be configured to allow pressurized oil to flow from recess 150 via passageways (not shown) in shell 100 into slot 204. In one exemplary embodiment, a size of inlet 216 may be selected to allow a metered amount of oil to flow through inlet 216 first thrust bearing face 142.

Thrust pad 206 may be located adjacent trailing end 202 of thrust pad section 196. Thrust pad 206 may extend between an inner edge 218 and an outer edge 220, forming a generally flat surface in a plane orthogonal to rotational axis 60. For example, inner edge 218 may be circumferentially spaced closer to outer edge 220 adjacent inner wall 192 as compared to adjacent outer wall 194. Outer edge 220 of thrust pad 206 may abut drain 198. Thrust pad 206 may have a generally flat surface which may be disposed generally orthogonal to rotational axis 60.

Ramp 208 may extend circumferentially from adjacent slot 204 to thrust pad 206. FIG. 4 illustrates a cut-away view showing portions of thrust pad section 196. As illustrated in FIG. 4, ramp 208 may extend from leading edge 222 adjacent slot 204 to trailing edge 224 that abuts inner edge 218 of thrust pad 206. Ramp 208 may have a generally flat surface, which may be disposed at an angle relative to thrust pad 206. For example, ramp 208 may be disposed at an axial depth “h₁” adjacent slot 204 and at an axial depth “h₂” adjacent thrust pad 206. In one exemplary embodiment as shown in FIG. 4, axial depth h₂ may be smaller than axial depth h₁. Oil entering slot 204 via inlet 216 may sweep or flow over ramp 208 and thrust pad 206 before entering drain 198. As also shown in FIG. 4, rim 210 of thrust pad section 196 may extend circumferentially along outer wall 194 from adjacent slot 204 to adjacent thrust pad 206. Rim 210 may prevent oil sweeping over ramp 208 from flowing radially outward, thereby helping to generate increased thrust pressure on thrust pad section 196. Rim 210 may also help direct oil flow from ramp 208 towards drain 198.

Returning to FIG. 3, drain 198 may be disposed between adjacent thrust pad sections 196 and may circumferentially separate adjacent thrust pad sections 196. For example, drain 198 may extend circumferentially from a trailing end 202 of a thrust pad section 196 to a leading end 200 of an adjacent thrust pad section 196. Drain 198 may also extend radially from adjacent inner wall 192 of thrust pad section 196 to adjacent flange outer surface 114. In one exemplary embodiment as illustrated in FIG. 3, drain 198 may have a generally rectangular channel cross section. It is contemplated, however, that drain 198 may have a cross-section of square, semi-circular or any other shape known in the art. FIG. 5 illustrates another cut-away view of thrust pad section 196. As illustrated in FIG. 5, drain 198 may have a first axial depth “h₃” along rotational axis 60 adjacent inner wall 192 of thrust pad section 196. Drain 198 may have a second axial depth “h₄” adjacent flange outer surface 114. In one exemplary embodiment as illustrated in FIG. 5, axial depth h₄ may be smaller than axial depth h₃. Drain 198 may help to drain the metered amount of oil dispensed via inlet 216 by directing the oil radially outward and away from first thrust bearing face 142. Dispensing and draining a metered amount of oil from each thrust pad section 196, may help ensure that dual thrust bearing 50 does not experience excessive thrust pressure on first thrust bearing face 142.

FIG. 6 illustrates a cut-away view showing details of second thrust bearing face 146 of dual thrust bearing 50. Second thrust bearing face 146 may extend radially between an inner wall 232 and an outer wall 234. Inner wall 232 may have a diameter smaller than a diameter of outer wall 234. Like first thrust bearing face 142, second thrust bearing face 146 may also include a plurality of thrust pad sections 236 circumferentially disposed on second thrust bearing face 146. Adjacent thrust pad sections 236 on second thrust bearing face 146 may be circumferentially separated by radially extending drains 238. Each thrust pad section 236 may include slot 240, thrust pad 242, ramp 244, and rim 246, each of which may have a structure and function similar to slot 204, thrust pad 206, ramp 208, and rim 210, respectively, as described above with respect to first thrust bearing face 142. Like slot 204, slot 240 may also include an inlet 250 disposed within slot 240 and configured to dispense pressurized oil to slot 240. Drain 238 may extend radially from adjacent inner wall 232 of thrust pad section 236 to adjacent outer wall 234. Drain 238 may have a structure and function similar to that of drain 198 as described above with respect to first thrust bearing face 142.

INDUSTRIAL APPLICABILITY

The disclosed dual thrust bearing 50 may be implemented in any turbocharger 10 in which shaft 16 is subjected to axial and radial loads during operation. The disclosed dual thrust bearing 50 may offer a compact bearing assembly 18 that includes a journal bearing 52 to help support radial loads on shaft 16 and a dual thrust bearing 50 to help support axial loads produced by compressor stage 12 and turbine stage 14.

Disposing journal bearing 52 between first and second thrust bearing faces 142, 146 of dual thrust bearing 50 may also help reduce a volume of bearing housing 38 required to accommodate bearing assembly 18. Additionally, attaching dual thrust bearing 50 to wall 74 of bearing housing 38 via fasteners 82 may help reduce a number of portions of bearing housing 38 that may be required to engage with dual thrust bearing 50 to position dual thrust bearing 50 within bearing housing 38. Reducing the number of portions of bearing housing 38 that engage with dual thrust bearing 50 may help relax machining tolerances on bearing housing 38 by reducing the number of portions of bearing housing 38 required to be concentric with shaft 16 and dual thrust bearing 50. The disclosed dual thrust bearing 50 may also help reduce or eliminate damage to bearing housing 38 in the event of a failure of compressor impeller 22. Failure of compressor impeller 22 may cause off-axis rotation of impeller cap 56, causing shaft portion 168 of impeller cap 56 to come into contact with journal inner surface 156. Further, the off-axis rotation may cause impeller step face 172 and thrust washer front face 182 to come into contact with first and second thrust bearing faces 142, 146, respectively. Such contact may cause mechanical damage to journal bearing 52, alignment pin 54, and first and second thrust bearing faces 142, 146 of dual thrust bearing 50. However, because dual thrust bearing 50 remains securely fastened to bearing housing 38 via fasteners 82, little to no damage may be imparted to first and second bores 70, 72, wall 74, or other surfaces of bearing housing 38. Reducing or eliminating the damage caused to bearing housing 38 may help to reduce the expense and the amount of time required to repair turbocharger 10.

A temperature of the oil may increase as the oil flows over journal outer surface 154, journal inner surface 156, and first and second thrust bearing faces 142, 146. The disclosed dual thrust bearing 50 may help to reduce an amount of increase in oil temperature. Referring to FIGS. 2, 3, and 6, during operation of turbocharger 10, pressurized oil may flow from recess 150 via passageways in shell 100 to journal outer surface 154 and first and second thrust bearing faces 142, 146. Pressurized oil may also flow axially along journal inner surface 156 to first and second thrust bearing faces 142, 146. The oil may wipe across ramps 208 and thrust pads 206 of a thrust pad section 196 of first thrust bearing face 142 and flow into drains 198 without wiping over the surfaces of an adjacent thrust pad section 196. Oil may similarly flow over a thrust pad section 236 of second thrust bearing face 146 and flow into drain 238 without flowing over an adjacent thrust pad section 236 of second thrust bearing face 146. By preventing a flow of oil over more than one thrust pad section 196 or 236, the disclosed dual thrust bearing 50 may help to reduce an amount of heating of the oil as the oil flows over first and second thrust bearing faces 142, 146.

The disclosed dual thrust bearing 50 may also help to cool bearing housing 38, which in turn may help to reduce temperature of both the compressor impeller 22 and bearing housing adjacent to the turbine journal bearing 20. For example, heat generated through compressing intake air may increase a temperature of compressor impeller 22, compressor housing 24, and bearing housing 38. Compressor impeller 22 may be further heated by heat radiating back from compressor housing 24 and bearing housing 38 to compressor impeller 22. Rotation of impeller cap 56 and thrust washer 58 may impart centrifugal force on the oil in first and second gaps 144, 148. Drains 198 and 238 may help to fling the oil radially outward towards the walls of bearing housing 38 to provide improved cooling of bearing housing 38 during operation of turbocharger 10. Cooling bearing housing 38 in this manner may help to reduce heating of compressor impeller 22, which may help to increase the operating life of compressor impeller 22.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed dual thrust bearing. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed dual thrust bearing. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

What is claimed is:
 1. A dual thrust bearing, comprising: a shell extending from a compressor end to a turbine end opposite the compressor end, the shell including: a shell bore extending from the compressor end to the turbine end, the shell bore being configured to receive a journal bearing; a first thrust bearing face disposed adjacent the compressor end; and a second thrust bearing face disposed adjacent the turbine end.
 2. The dual thrust bearing of claim 1, wherein the shell further includes a flange disposed adjacent the compressor end, the flange is configured to attach the dual thrust bearing to a bearing housing, and the first thrust bearing face is disposed on the flange.
 3. The dual thrust bearing of claim 2, wherein the first thrust bearing face includes a plurality of thrust pad sections disposed circumferentially on the first thrust bearing face, each thrust pad section extending circumferentially from a leading end to a trailing end and extending radially from an inner wall to an outer wall.
 4. The dual thrust bearing of claim 3, wherein the thrust pad sections include: a first thrust pad section; a second thrust pad section; and a drain separating the first thrust pad section from the second thrust pad section, the drain extending radially from adjacent the inner wall to a flange outer surface.
 5. The dual thrust bearing of claim 4, wherein the drain has a first axial depth adjacent the inner wall and a second axial depth smaller than the first axial depth adjacent the outer surface of the flange.
 6. The dual thrust bearing of claim 3, the thrust pad section includes: a slot disposed adjacent the leading end; a thrust pad disposed adjacent the trailing end; and a ramp disposed between the slot and the thrust pad.
 7. The dual thrust bearing of claim 6, wherein the ramp has a first axial depth adjacent the slot and a second axial depth smaller than the first axial depth adjacent the thrust pad.
 8. The dual thrust bearing of claim 6, wherein the thrust pad section further includes a rim extending circumferentially along the outer wall from adjacent the slot to adjacent the thrust pad.
 9. The dual thrust bearing of claim 6, wherein the slot extends radially from an inner slot end disposed adjacent the inner wall to an outer slot end disposed adjacent the outer wall, and the slot includes an inlet disposed adjacent the inner slot end, the inlet being configured to dispense a metered amount of oil into the slot.
 10. A bearing assembly, comprising: a shell extending from a compressor end to a turbine end opposite the compressor end; a shell bore extending from the compressor end to the turbine end; a first thrust bearing face disposed on the compressor end of the shell; a second thrust bearing face disposed on the turbine end of the shell; and a journal bearing disposed within the shell bore.
 11. The bearing assembly of claim 10, further including: an impeller cap having a cap portion, a shaft portion disposed within the journal bearing, an impeller cap bore, and an impeller step face; a shaft disposed within the impeller cap bore; and a thrust washer disposed on the shaft adjacent the turbine end.
 12. The bearing assembly of claim 11, wherein the impeller step face is disposed opposite the first thrust bearing face and axially separated from the first thrust bearing face by a first gap; and the thrust washer has a thrust washer front face disposed opposite the second thrust bearing face and being axially separated from the second thrust bearing face by a second gap.
 13. The bearing assembly of claim 10, further including a flange configured to mount the shell to a bearing housing, the first thrust bearing face being disposed on a portion of the flange.
 14. The bearing assembly of claim 13, further including: a wall of the bearing housing, the wall having a front face and a rear face; a fastener hole extending from the front face to the rear face; a backing plate disposed adjacent the rear face; and a fastener extending through the flange and the wall and threadingly engaged with the backing plate to mount the shell to the bearing housing.
 15. The bearing assembly of claim 14, further including: an alignment cavity in the wall, the alignment cavity extending from the front face towards the rear face; and an alignment pin extending from a knob portion to a stud portion, the knob portion being received in the alignment cavity and the stud portion being received in a pin recess in the journal bearing.
 16. The bearing assembly of claim 13, wherein the first thrust bearing face includes a plurality of thrust pad sections disposed circumferentially on the first thrust bearing face, each thrust pad section extending circumferentially from a leading end to a trailing end and extending radially from an inner wall to an outer wall.
 17. The bearing assembly of claim 16, wherein the thrust pad section includes: a slot disposed adjacent the leading end; a thrust pad disposed adjacent the trailing end; and a ramp disposed between the slot and the thrust pad.
 18. The bearing assembly of claim 17, wherein the ramp has a generally flat surface disposed at an angle relative to the thrust pad.
 19. The bearing assembly of claim 16, wherein the thrust pad sections include: a first thrust pad section; a second thrust pad section; and a drain separating the first thrust pad section from the second thrust pad section, the drain extending radially from adjacent the inner wall to a flange outer surface.
 20. A turbocharger, comprising: a turbine housing; a turbine wheel disposed within the turbine housing and configured to be rotated by exhaust received from an engine; a compressor housing; a shaft attached to the turbine wheel, the shaft extending from the turbine housing to the compressor housing; a compressor impeller disposed within the compressor housing, the compressor impeller being configured to be driven by the turbine wheel via the shaft; a bearing housing connecting the turbine housing with the compressor housing; a bearing assembly disposed within the bearing housing, the bearing assembly including: a shell extending from a compressor end to a turbine end; a shell bore in the shell extending from the compressor end to the turbine end; a journal bearing extending from the compressor end to the turbine end, the journal bearing being disposed within the shell bore; a thrust washer disposed on the shaft adjacent the turbine end; a first thrust bearing face disposed on the compressor end of the shell, the first thrust bearing face being axially separated from the compressor impeller by a first gap; and a second thrust bearing face disposed on the turbine end of the shell, the second thrust bearing face being axially separated from the thrust washer by a second gap. 